If marine organisms adhere and grow on the water-contact regions of industrial aquatic equipment, water-intake equipment of atomic power plants or the like, marine structures, ships, etc., various damages are brought about. Particularly in cooling water-intake channels of power plants, growth of marine organisms increases flow resistance of running seawater for cooling, and as a result the function of a heat exchanger is lowered and evil influence is exerted on power generation efficiency. Then, an antifouling coating film is formed on a surface of a base to prevent adhesion of marine organisms. As such an antifouling coating film, an antifouling composite coating film constituted of an epoxy undercoating film and a silicone finish coating film has been employed. This composite coating film, however, has poor adhesion between the finish coating film and the undercoating film and has a problem of durability of the water-contact region. Therefore, an intermediate coating film (binder layer) is provided between the undercoating film and the finish coating film to improve adhesion (e.g., patent documents 1 and 2).
In this method, however, it takes a long time to form the antifouling coating film because the intermediate coating film is formed. Moreover, there still resides a problem of anticorrosion property though the adhesion between the undercoating film and the finish coating film has been improved.
As a means to solve such a problem, there has been disclosed a composite antifouling coating film in which an undercoating film of a vinyl ester resin or an unsaturated polyester resin and a silicone resin antifouling coating film are formed in order on a surface of a base (e.g., patent document 3) or a composite coating film in which an undercoating film composed of an undercoating composition containing a block polymer constituted of organosiloxane units and alkylene oxide units and having polar groups at both ends of a molecule and a finish coating film composed of a silicone rubber finish coating composition are formed in order on a surface of a base (e.g., patent document 4).
According to such a composite coating film, the production process can be shortened because an intermediate coating film is not formed, and the adhesion between the undercoating film and the finish coating film can be improved. However, there is yet room for improvement in the anticorrosion property.
On the other hand, an anticorrosive coating composition comprising (a) an epoxy resin, (b) a curing agent, (c) a coumarone resin and (d) a hydroxyl group-containing terpenephenol resin and a coating film formed from the composition have been disclosed in a patent document 5. In this document 5, however, there is neither description nor suggestion of adhesion of this coating film to other coating films, particularly to an organopolysiloxane antifouling coating film.
Patent document 1: Japanese Patent No. 1046338
Patent document 2: Japanese Patent No. 1276889
Patent document 3: Japanese Patent Laid-Open Publication No. 296175/1998
Patent document 4: Japanese Patent Laid-Open Publication No. 327914/2001
Patent document 5: Japanese Patent Laid-Open Publication No. 279167/2001